Back to basics: YDNA

Reader Frank Folwell Jr. would sure like to get some help with a part of his family tree.

“I have traced my Folwell line to colonial New Jersey,” he writes:

William Folwell of Salem, N.J., d. 1710 is most likely my immigrant ancestor.

There were two other male Folwells in N.J. in the late 1600s (colonial records). Family legend says the three were brothers (Nathan and Peter) who came from England. Nathan’s extensive family tree is well documented.

My question: If I have my DNA tested and if a known male descendant of Nathan did the same, could it prove that we are of the same family line? William and Nathan are eight or nine generations back.

Great question, and one The Legal Genealogist doesn’t see nearly enough with all the emphasis these days on those blankety-blank-blank percentages from autosomal DNA tests.1

The kind of DNA Frank is talking about is YDNA — the DNA passed from father to son to son only through the direct male line. So it’s the type that is “used to explore a man’s patrilineal or direct father’s-line ancestry” because the Y chromosome, which only men have, “passes down virtually unchanged from father to son.”2 It’s one of the basic building blocks of genetic genealogy.

And yes, absolutely, if Frank and a known direct-male-line descendant of Nathan Folwell both took a YDNA test, and if they match at a high level, that can be definitive evidence that the two Folwell lines have a common root: some male somewhere back in time from which they both descend.

If the two took a 37-marker YDNA test and matched 37-for-37, the testing company that features YDNA testing, Family Tree DNA, would regard them as very tightly related: “A 37/37 match between two men who share a common surname (or variant) means they share a common male ancestor. Their relatedness is extremely close with the common ancestor predicted, 50% of the time, in five generations or less and over a 95% probability within eight generations. Very few people achieve this close level of a match. All confidence levels are well within the time frame that surnames were adopted in Western Europe.”3

A match of 36-for-37 markers puts them into the tightly related category; 34- or 35-for-37 into the related category; and 33-for-37 into the probably related category. At 32-for-37, the two men would be regarded as possibly related and at 31-for-37, not related.4

If both tested at a higher level, say, 67 markers, a 67-for-67 marker match puts them into the very tightly related group: “A 67/67 match between two men who share a common surname (or variant) means they share a common male ancestor within the genealogical time frame. Their relatedness is extremely close. All confidence levels are well within the time frame that surnames were adopted in Western Europe with the common ancestor predicted, 50% of the time, in three generations or less and with a 90% probability within five generations. Very few people achieve this close level of a match.”5

A match of 65- or 66-for-67 markers puts them into the tightly related category; 61-, 62-, 63- or 64-for-67 into the related category; and 60-for-67 into the probably related category. At 58- or 59-for-67, the two men would be regarded as only possibly related and beyond that, not related, at least not within a genealogical time frame.6

So YDNA can definitely provide evidence of a relationship.

But, of course, there’s a hitch.

Two hitches, in fact.

The first is, if they do match, the test can’t tell the two men exactly how they’re related, or who the common ancestor is. It can tell them they are both descended from one man, somewhere back in time, but — by itself, without paper trail evidence — can’t put a name on that man. They could both be descended from the man who fathered William and Nathan and Peter. Or from the grandfather. Or the great grandfather. Or from William. Or from Nathan. Or from Peter. Or from any male in the same direct male line of descent.

So it would prove they were both Folwells from a common Folwell ancestor — but won’t by itself prove who that Folwell was.

The second is, if they don’t match, it won’t tell them why they don’t match. It could be that there’s more than one Folwell line here: two groups of immigrants reaching America around the same time with the same name, but not the same origins in England.

Or it could be there’s an unrecorded adoption somewhere in the male line for one of the two that breaks the DNA chain — a step-son could have taken his step-father’s name early on and carried forward the Folwell name but not the Folwell YDNA.

And there could even be a very recent case of … um … let’s just call it misattributed paternity, shall we?

Any of those would be possible as theories, and without testing more than just those two men, none of them could be ruled out.

As long as everybody understands what YDNA can — and can’t — show, it’s a great way to shed light on family history.

Yes, YDNA is going back to basics — and that can be a very good thing.

SOURCES

If I see one more question about tracing that family story about ancestry of the (whatever-the-flavor-of-the-month-is) and why it doesn’t show up in the ethnicity estimates, I may scream. No, you should not swap your lederhosen for a kilt. See Judy G. Russell, “Admixture: not soup yet,” The Legal Genealogist, posted 18 May 2014 (https://www.legalgenealogist.com/blog : accessed 30 July 2016). ↩

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17 Comments

Jay Fonkert on July 31, 2016 at 6:54 pm

Indeed! Everyone is talking about autosomal — for obvious reasons. But, it seems like Y-DNA has been forgotten. I’m working on a lecture that starts with Y-DNA, and goes to autosomal for backup evidence. This particular case is not a slam dunk, but with not direct documentary evidence, it expands my evidence base.

Just to chime in, my surname is a County Mayo unique variant of McGinn but growing up I’ve been told that the majority of McGing’s I’ve met in the US and Ireland were not related. How could that be, I wondered? So, here comes Y-DNA testing. So far, there are 3 of us who have tested, myself and 2 McGing or McGinn named men who come from lines where we have no record of being connected to me. And bingo, we all show us as tightly related to each other. So while we will never know who this common ancestor was (Irish records in the West being what they are) we now know that indeed it’s very likely we are indeed cousins. With some further testing of the other “non-related” McGing lines, we may be able demonstrate that if your surname is McGing, we likely are cousins, even if we can’t say via whom. I’ll take that as a win 🙂

I was told by a gentleman manning the MacGregor clan tent at a Scottish festival that the MacGregor clan organizations might be setting up a Y-DNA project to try to confirm whether a number of different surnames are actually aliases adopted by MacGregors while the clan was famously outlawed and persecuted during most of the 1600s and 1700s. At the time, many MacGregors were forced to adopt new surnames in order to survive and although information about their original identity was sometimes passed down orally within the family, this information was kept secret from outsiders and did not appear in the written records.https://en.m.wikipedia.org/wiki/Clan_Gregor

I want my 69-year-old dad to test his yDna. It would be for possible future use as at this point we don’t have a specific question we need answered. Which level of markers would be the best to test? Is the 111 marker test worth the extra money?

Thank you for your insight! I am a student at the National Institute for Genealogical Studies and the holder of a B.S. in Zoology with emphasis in cellular and molecular biology. I have to take the genealogical DNA classes in several months, so I only have rudimentary knowledge of the genealogical DNA testing process. I have many questions about the genealogical tests due to my molecular biology experience, and have been trying to find someone to ask who would not be offended by my questions. You just pointed out some of the hitches I was curious about in the tests. I had hoped those hitches were known at some level of genealogical DNA testing. Thank you!

I absolutely agree. DNA is one of many great tools in our genealogy toolbox. I see many people who treat it as a panacea, hence my caution in asking just anyone about hitches. (grin)

Noél Emswiler on August 1, 2016 at 10:57 pm

Does it matter when comparing Y-DNA what level of testing each male did? For example my husband did the Y-DNA 111 and matches with another male who did the Y-DNA 37 with a genetic distance of zero. Am I correct to believe that this is a strong match? Or is there something I am missing?

It’s a strong match but only at the 37-marker level. You have no way of knowing if it remains a strong match beyond that because the other man didn’t test beyond that level. So it’s a very good match, but particularly if it’s a common haplogroup, and common surname, it could fall apart by 67 or 111 markers.

Y-DNA testing helped break through a brick wall on my paternal line about a year ago, and it turned out be a case of – ahem – misattributed paternity. My surname is Jenkins, but all of my Y-DNA matches were named Smith. After several years of being stumped by this, about a year ago I was alerted to a new match who was able to finally provide some answers. In this case, it turns out there was an affair between my 3G grandfather (S. Smith) and one of his wife’s sisters (we don’t know which one in particular, but their surname was Jenkins). Since it was an illegitimate birth, the infant boy (my great-great grandfather) was given his mother’s surname of Jenkins instead of Smith like his father. The story was kept quiet, at least on our side of the family, so my father and grandfather knew nothing about it. Fortunately my Y-DNA match had heard the story passed down through his side of the family and was able to illuminate it for us! There’s even more to the story that makes it even more interesting and compelling, but I’ll save that for another forum. So the good news is Y-DNA helped us solve this mystery; the bad news is I now have the great challenge of continuing my paternal research along the oh-so-common Smith surname! 🙂

I’m attempting to use autosomal results to help in the analysis of a gentleman in the J1-ZS241 sub project. The question has to do with large segment pileups on chromosome 19. Thomas is in a Kohanim cluster and has no known Jewish ancestry. He traces his tree to mid 1700s Virginia and believes his deeper ancestry is Scottish. He has a few Jewish 3-5 cousin autosomal matches. All of these matches have a large segment pileup on chromosome 19 with Thomas. I’ve been trying to find out if this is IBS or IBD (and have posted this question everywhere!) I’d greatly appreciate any ideas you may have.

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